Influence of calcium macronutrient on tip burn occurrence in hydroponically cultivated lettuces

Abstract

Tip burn in hydroponics lettuce is an undesirable phenomenon identified by necrotic breakdown of marginal tissue of leaves. A deep-water culture hydroponics system was designed to determine the effect of increasing nutritional calcium concentration and varying nutritional calcium sources in alleviating the tip burn development for the hydroponics growth of lettuce (Lactuca sativa). Lettuces was cultivated separately in an untreated fish wastewater (150mg/L) and four treated fish wastewaters with calcium addition by calcium hydroxide and calcium carbonate to concentrations of 250 and 350mg/L respectively. Increasing calcium concentration from 150 to 350mg/L demonstrated not only an increase in tip burn incidence by 33.33% (calcium carbonate) and 50% (calcium hydroxide), but a slower plant growth in comparison with lettuces cultivated at 150mg/L. Besides, lettuces treated by calcium carbonate has greater leaf calcium concentrations by 48.17% at constant calcium concentration, attributed to its high solubility to release more Ca2+ ions in fish wastewater for plant adsorption. Results suggest that the addition of calcium carbonate to fish wastewater for hydroponics cultivation is more suitable for reducing the tip burn occurrence and growth inhibition at concentrations up to 150mg/L.